/**
 * CRC32(cyclic redundancy check) implements functions.
 * 	define in header file src/cel_hash.h.
 *	@package src/cel_crc32.c
 * 
 * @author chenxin <chenxin619315@gmail.com>
 */
#include "cel_hash.h"
#include <stdio.h>
#include <stdlib.h>

#ifdef _MSC_VER  
typedef __int32 int32_t;  
typedef unsigned __int32 uint32_t;  
typedef __int64 int64_t;  
typedef unsigned __int64 uint64_t;  
#else  
#include <stdint.h>  
#endif 

//crc32 polynomial
#define POLYNOMIAL_CRC32 0x04c11db7L

/**
 * crc32 quick driven table.
 * 	generated by function create_crc32_table
 * 	and print by function print_crc32_table.
 */
static const uint32_t crc32_table[256] = {
    0x00000000, 0x04c11db7, 0x09823b6e, 0x0d4326d9, 
    0x130476dc, 0x17c56b6b, 0x1a864db2, 0x1e475005, 
    0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61, 
    0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd, 
    0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9, 
    0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75, 
    0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011, 
    0x791d4014, 0x7ddc5da3, 0x709f7b7a, 0x745e66cd, 
    0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039, 
    0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5, 
    0xbe2b5b58, 0xbaea46ef, 0xb7a96036, 0xb3687d81, 
    0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d, 
    0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49, 
    0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95, 
    0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1, 
    0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d, 
    0x34867077, 0x30476dc0, 0x3d044b19, 0x39c556ae, 
    0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072, 
    0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16, 
    0x018aeb13, 0x054bf6a4, 0x0808d07d, 0x0cc9cdca, 
    0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde, 
    0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02, 
    0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1, 0x53dc6066, 
    0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba, 
    0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e, 
    0xbfa1b04b, 0xbb60adfc, 0xb6238b25, 0xb2e29692, 
    0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6, 
    0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a, 
    0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e, 
    0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2, 
    0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686, 
    0xd5b88683, 0xd1799b34, 0xdc3abded, 0xd8fba05a, 
    0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637, 
    0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb, 
    0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f, 
    0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53, 
    0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47, 
    0x36194d42, 0x32d850f5, 0x3f9b762c, 0x3b5a6b9b, 
    0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff, 
    0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623, 
    0xf12f560e, 0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7, 
    0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b, 
    0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f, 
    0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3, 
    0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7, 
    0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b, 
    0x9b3660c6, 0x9ff77d71, 0x92b45ba8, 0x9675461f, 
    0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3, 
    0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640, 
    0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c, 
    0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8, 
    0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24, 
    0x119b4be9, 0x155a565e, 0x18197087, 0x1cd86d30, 
    0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec, 
    0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088, 
    0x2497d08d, 0x2056cd3a, 0x2d15ebe3, 0x29d4f654, 
    0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0, 
    0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c, 
    0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18, 
    0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4, 
    0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0, 
    0x9abc8bd5, 0x9e7d9662, 0x933eb0bb, 0x97ffad0c, 
    0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668, 
    0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4, 
};


//create the crc32 table
//static void create_crc32_table()
//{
//    register ushort_t i, j;
//    register uint32_t crc;
//
//    for ( i = 0; i < 256; i++ ) 
//    {
//	crc = ( (uint32_t)i << 24);
//	for ( j = 0; j < 8; j++ ) 
//	{
//	    if ( (crc & 0x80000000L) != 0 )
//		crc = (crc << 1) ^ POLYNOMIAL_CRC32; 
//	    else
//		crc = (crc << 1);
//	}
//	crc32_table[i] = crc;
//    }
//}

//print the crc32 table
//static void print_crc32_table( uint32_t * table, char * name )
//{
//    register uint_t i = 0,j;
//    printf("static const uint32_t %s[256] = {\n", name);
//    while ( i < 256 ) {
//	for ( j = 0; j < 4; j++ ) {
//	    printf("0x%x, ", table[i + j]);
//	}
//	printf("\n");
//	i += 4;
//    }
//    printf("};\n");
//}

/**
 * CRC32 hash algorithm.
 * 	cyclic Redundancy check.
 */
CEL_API uint32_t cel_crc32( uint32_t crc, const void * data, size_t length )
{
    register uint_t i,j;

    /* you may use the following two functions to generate 
     * 	the above the lookup table,
     * after the calculation, we don't need the two functions
     * any more. yeah, we use if only once.
     */
    //create_crc32_table();
    //print_crc32_table(crc32_table, "crc32_table");
    uchar_t * str = ( uchar_t * ) data;

    for ( i = 0; i < length; i++ ) 
    {
	   j = ((int)(crc >> 24) ^ *str++) & 0xFF;
	   crc = (crc << 8) ^ crc32_table[j];
    }
    crc = ~crc;

    return crc;
}

//we use a macro define instead.
//CEL_API uint32_t cel_crc32_hash( const char * str )
//{
//    return 0;
//}

#define BUFSIZE 2048
/**
 * generate a crc32 code for a specified file.
 *
 * @param	file
 * @return	uint32_t
 */
CEL_API void cel_crc32_file( 
	const char * _file,
	uint32_t * file_crc32 )
{
    FILE * stream;
    char buffer[BUFSIZE];
    uint32_t crc = 0xffffffff;

    //open the file.
    if ( ( stream = fopen(_file, "r") ) == NULL ) 
    {
    	printf("Error: unable to open file %s\n", _file);
    	*file_crc32 = crc;
    	return;
    }

    //read and count the crc32 code.
    while ( fgets(buffer, BUFSIZE, stream) != NULL )
    {
	   //printf("buffer: %s\n", buffer);
	   crc = cel_crc32( crc, buffer, strlen(buffer) );
    }
    *file_crc32 = crc;

    //close the file stream.
    fclose(stream);
}

